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Converted iris cells could restore damaged retinas

By Emma Young

Iris cells can be tweaked to imitate retinal cells, raising the prospect of using a patient’s own tissue to treat damaged retinas, say Japanese researchers.

In the developing eye, the inner layer of the “optic cup” differentiates into the retina and the iris. “This common developmental origin prompted us to test whether iris tissue could give rise to retinal tissue,” Masayo Takahashi of Kyoto University and his colleagues write in the journal Nature Neuroscience.

The team extracted iris tissue from adult rats’ eyes, a relatively straightforward procedure. Then they used a modified virus to introduce into the cells a master switch gene expressed in mature light-reactive cells in the retina.

They found that the cells produced rhodopsin, the light-sensitive pigment contained in rod photoreceptor cells in the retina. Ultimately, the team hope that iris cells could be coaxed into producing rhodopsin using chemical factors, rather than gene therapy.

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Stem cell failure

“Our results have opened up the possibility of autograft of photoreceptor cells, however we still have a long way to go,” Takahashi told New Scientist.

Autografts involve removing a section of tissue from a patient and grafting it somewhere else on their body. Retinal transplants from one person to another are currently performed, but there is a severe lack of donors. The potential for immune system rejection of the transplanted tissue is also a problem.

Iris cells offer the best hope for retinal autografts, says Takahashi. Attempts to create photoreceptors from neural stem cells, for example, have so far failed.

Age-related macular degeneration, which involves a wearing out of light-sensitive rod and cone cells, is one of the commonest causes of blindness in the west and affects 30 per cent of people over 75. The only cure is to transplant healthy cells into the damaged area.